A number of systems and programs are offered on the market for the design, the engineering and the manufacturing of objects. CAD is an acronym for Computer-Aided Design, e.g. it relates to software solutions for designing an object. CAE is an acronym for Computer-Aided Engineering, e.g. it relates to software solutions for simulating the physical behavior of a future product. CAM is an acronym for Computer-Aided Manufacturing, e.g. it relates to software solutions for defining manufacturing processes and operations. In such systems, the graphical user interface (GUI) plays an important role as regards the efficiency of the technique. These techniques may be embedded within Product Lifecycle Management (PLM) systems. PLM refers to a business strategy that helps companies to share product data, apply common processes, and leverage corporate knowledge for the development of products from conception to the end of their life, across the concept of extended enterprise.
The PLM solutions provided by Dassault Systèmes (under the trademarks CATIA, ENOVIA and DELMIA) provide an Engineering Hub, which organizes product engineering knowledge, a Manufacturing Hub, which manages manufacturing engineering knowledge, and an Enterprise Hub which enables enterprise integrations and connections into both the Engineering and Manufacturing Hubs. All together the system delivers an open object model linking products, processes, resources to enable dynamic, knowledge-based product creation and decision support that drives optimized product definition, manufacturing preparation, production and service.
Some CAD systems now deal with packaging design. Packaging design systems may typically allow to define the shape of a flat carton board sheet and the arrangement of bend lines on said sheet in such a way that, according to a folding procedure, which may also be a matter of packaging design, the flat sheet changes itself into a three dimensional box that is able to contain some kind of goods. Packaging design CAD systems include for example ArtiosCAD software (registered trademark). ArtiosCAD includes geometric tools for a user to interactively define the outside shape, bend lines and panels of a flat carton board sheet as well as the folding procedure and the resulting three-dimensional shape of the package. For the sake of comprehensiveness, it is noted that ArtiosCAD also includes other functions related to packaging design (drawing, artwork, flexible package, layout for manufacturing) that are out of the scope of the present discussion.
FIG. 1 illustrates the typical flat view of a three dimensional box, carton board sheet 100, designed by ArtiosCAD. Dotted lines represent bend lines. Solid lines represent boundaries of the planar carton board sheet. Portions of sheet 100 bounded by dotted and/or solid lines are named panels. By definition, two panels are said to be adjacent if they share a bend line. Panels are numbered from 1 to 13 in the figures. FIG. 2 illustrates three-dimensional box 200 obtained by folding carton board sheet 100 of FIG. 1. Only visible panels of FIG. 1 are tagged with numbers on FIG. 2.
The key point of state of the art packaging design systems is related to the bend lines arrangement: each bend line can be folded independently. Formally, this means that the panels' adjacency graph is acyclic. The panels' adjacency graph is a non-directed graph defined as follows. Vertices are panels' numbers and arcs capture the adjacency relationship: an arc joins panel number i and panel number j if the said panels are adjacent (meaning that they share a bend line). From the mathematical point of view, the flat carton board sheet corresponds to a planar graph and the panels' adjacency graph is its dual graph. FIG. 3 illustrates panels' adjacency graph 300 of carton board sheet 100 of FIG. 1. It is clearly acyclic. The technical consequence is that the folding procedure can be directly computed by choosing a base panel on the flat sheet and by traversing the acyclic graph.
As opposed to the acyclic graph, the theoretical case of a local cycle in the panels' adjacency is not handled by the prior art in a satisfactory way. The corresponding significant folding situation is characterized when at least four bend lines are concurrent at a point P and when no boundary line meets point P. It is well known from state of the art that folding is generally impossible with three or less concurrent bend lines. Furthermore, it is well known from state of the art that folding is generally impossible when bend lines in such a cycle are not concurrent and not parallel (parallelism is discussed later).
FIG. 4 illustrates sheet 400 having seven panels including four panels sharing concurrent bend lines (at point P) in a cyclic way. The corresponding adjacency graph 500 shown on FIG. 5 includes the cycle of arcs (1,2), (2,3), (3,4) and (4,1) caused by four concurrent bend lines. Clearly, panels adjacent to concurrent bend lines cannot be folded independently. For example, choose panel 1 as the fixed panel and rotate panel 4 upward around the bend line shared with panel 1. This causes panels 2 and 3 to move accordingly. The final position illustrated in FIG. 6 is such that panels 1 and 2 are in the same plane. Panels 5, 6 and 7 are folded independently. It must be understood that the cyclic situation and the folding conditions are not altered if carton board sheet 400 is punched by a hole in the neighborhood of point P, meaning that there is no material around point P. In particular, the panels' adjacency graph is unchanged. FIGS. 7-8 illustrate this situation with hole 700 around point P on sheet 750, which is otherwise the same as sheet 400 of FIG. 4.
As mentioned previously, a cyclic situation with folding is allowed by parallel bend lines, as illustrated by FIGS. 9-11 which respectively show the sheet when unfolded, the panel's adjacency graph, and the sheet after folding. The folding is made possible because the distance separating bend lines of panel 2 is equal to the distance separating bend lines of panel 4. This situation is out of the scope of the present discussion because it is not difficult to compute.
In this context, the invention aims at improving the design of a folded sheet object.